1. Field of the Invention
The present invention relates to a .heater unit for automobile air conditioner and more particularly improvement in prevention of window and air heating performance in DEF/foot mode operation of automatic air conditioner.
2. Description of the Prior Art
In recent years, for the purpose of the improvement in safe driving, automatic air conditioner has become used popularly for the automobile. In virtute of this system, only if a driver sets a desired temperature, then the temperature of the conditioned air, ON/OFF of compressor, selection appropriate one from outlet modes associated with control doors, intake of inside air and/or outside air, and air amounts can be automatically controlled.
Automobile air conditioning is accomplished under the control of temperature and other parameters of it by a control unit where data signalled from different sensors particularly of in-car sensor, ambient sensor, intake sensor, sun sensor, and water temperature sensor located as predetermined is referred to respective previously-specified values.
"Automobile air conditioning system" can be operated in the so-called outlet modes in each of which some are selected from a plurality of outlets provided in the heater unit according to in-car and ambient conditions. There is known an automatic air conditioner of which an outlet mode having two different opening angles. For example, defrost/foot (referred to as D/F hereinafter) mode is subdivided into I and II in which their ratios between blows through defrost and foot outlets is set to 2:8 and 3:7, respectively. Such subdivision of D/F mode comes because of preventing window inside clouding in the case of low ambient air temperature, and thus making it possible to blow a relatively large amount of hot air against window surface even in the case of reduced blow-off because of lowering in fan speed under automatic control by the automatic air conditioner. The construction therefore is provided that when the "target blowout temperature (Tm)" obtained based on input data from the aforesaid sensors is high, D/F mode I is selected, and additionally if ambient air temperature is low, D/F mode II is selected to blow a large amount of hot air against window inside surface compared with D/F mode I.
The above-stated automobile air conditioner operable in two D/F modes may be certainly effective to prevent window clouding at low ambient air temperatures by selecting D/F mode II and blowing off a large amount of hot air from defrost duct. In this case or at low ambient air temperatures, generally, the inside of the car is at low temperature, and for this reason, a large amount of hot air should be also blown at the feet of the drier or passengers. The prior automatic air conditioner will select one from D/F modes I and II in one significance depending only upon ambient air temperature, resulting in a small amount of hot air supplied at the feet compared with D/F mode I. This may be said poor control in aspect of air heating.
The inventors therefore have studied with intense effort to develop a heater unit for automobile air conditioner having satisfactory preventive effect on window clouding can achieved without needing to exceed a certain amount of hot air, and for another thing the amount of air fed by a fan is controlled depending on the "target blowout temperature", and as a result the present invention has been completed.